Climate change isn't simply making the world warmer on average, but by changing the temperature balance between the equator and the poles, it may be disrupting normal weather patterns. As a result of an unusually strong atmospheric blocking pattern over the North Atlantic, the first three weeks of March have been cooler than average. Some scientists think such blocking patterns in the jet stream are related to the melting of Arctic sea ice during recent summers.

March 20 marks the vernal equinox, although the weather may not feel much like spring with cooler than average temperatures in many parts of the country.

The conditions couldn’t be more different than last year this time. By March 19, 2012, more than 2,200 warm-temperature records had been set or tied across the U.S. That is about 1,000 more than have been set or tied so far this March. By comparison, this month feels like a dud. Temperatures have been much closer to normal this year, and more than a few winter storms have crept their way towards the first day of spring.

The graph above shows the month-to-date temperature anomaly in Albany for March 2012 (red) and March 2013 (green). As you can see, 2012 was significantly warmer than usual at this time of year, while March of 2013 has actually been a little colder than normal.

The maps below show the difference between these two months across the country. Areas like the Southeast and Midwest are cooler than they were last year, while regions like the West and Southwest are considerably warmer.

All told, 2013 is much closer to an average year than 2012 was. But a normal, or even a cold year, doesn’t mean that the process of global warming has slowed down. According to a draft of the latest National Climate Assessment report released in January, global annual average temperatures have climbed by more than 1.4°F since 1880, fueled in large part by human-caused greenhouse gases.